Conventionally, an air bag apparatus which is a vehicle occupant protection apparatus is widely used in view of protection of occupants of automobiles or the like. The airbag apparatus is provided for the purpose of protecting a vehicle occupant from shock caused by crash of a vehicle or the like. The airbag is instantaneously inflated and expanded at a time of crash of a vehicle or the like to serve as a cushion receiving the body of a vehicle occupant. A gas generator is equipment incorporated in this airbag apparatus to instantaneously generate gas at a time of crash of a vehicle or the like and inflate and expand the airbag.
Airbag apparatuses include a variety of constructions depending on the mounting positions on vehicles or parts of the body to be protected. For example, as for the airbag apparatus mounted on automobiles, a driver's airbag installed in front of the driver seat, a passenger's airbag installed in front of the passenger seat, a so-called side airbag or curtain airbag installed on a side of the driver seat or passenger seat, and the like are known. Therefore, gas generators incorporated in airbag apparatuses include a variety of constructions, and the most suitable construction is selected depending on specifications.
One of a variety of constructions of gas generators is a so-called T-shaped gas generator having a cylindrical housing with closed opposite ends and discharging gas from the opposite end portions. In the T-shaped gas generator, an ignition chamber in which an igniter and enhancer agent are stored is provided in the central position of the cylindrical housing, a pair of combustion chambers in which a gas generating agent is stored are provided on the opposite end portions of the cylindrical housing, between which the ignition chamber is sandwiched, and respective gas discharge openings in communication with the respective combustion chambers are separately provided. In this T-shaped gas generator, two gas output portions generating and outputting gas can be provided independently. Moreover, these two gas output portions can be driven by one igniter. The documents disclosing the T-shaped gas generator include, for example, Japanese Patent Laying-Open No. 8-26064 (Patent Document 1).
FIG. 23 is a cross-sectional view of a conventional T-shaped gas generator disclosed in the aforementioned Patent Document 1. As shown in FIG. 23, in a conventional T-shaped gas generator 101, a base member 110 and a support member 111 are arranged in the middle portion of a cylindrical housing 102 having opposite ends closed by closing members 141, 142. An igniter 112 and enhancer agent 114 are stored in an ignition chamber 113 defined by base member 110 and support member 111. On opposite outsides thereof, first and second combustion chambers 123, 133 in which gas generating agents 124, 134 are stored are respectively arranged such that ignition chamber 113 is sandwiched therebetween. On the further outsides thereof, first and second filter chambers in which filter members 125, 135 are stored are respectively arranged. Ignition chamber 113 in which enhancer agent 114 is stored and first and second combustion chambers 123, 133 in which gas generating agents 124, 134 are stored are communicated with each other respectively through a first transfer path 115 and a second transfer path 116 provided to base member 110. Then, gas discharge openings 122, 132 for discharging the generated gas are provided on the circumferential surface of housing 102 at the portions defining the first and second filter chambers, whereby gas output portions 121, 131 are provided at the opposite end portions of cylindrical housing 102.
In the aforementioned conventional T-shaped gas generator 101, igniter 112 is actuated at a time of vehicle crash to ignite and burn enhancer agent 114 in ignition chamber 113, and hot particles produced by combustion of enhancer agent 114 pass through first transfer path 115 and second transfer path 116 to respectively flow into first combustion chamber 123 and second combustion chamber 133, whereby gas generating agents 124, 134 stored in first combustion chamber 123 and second combustion chamber 133 are respectively fired and burned. The combustion of gas generating agents 124, 134 causes a large amount of gas to be generated in first and second combustion chambers 123, 133, and the generated gas respectively passes through filter members 125, 135 stored in the first filter chamber and the second filter chamber to be discharged to the outside of housing 102 from gas discharge openings 122, 132. Then, the gas discharged from housing 102 inflates and expands the airbag. Patent Document 1: Japanese Patent Laying-Open No. 8-26064